Nitinol ice blades

ABSTRACT

A Nitinol ice blade includes a blade body having attachment structure by which it is held in a blade holder of an ice ravel device, such as an ice skate or ice boat. The processes and products made by the processes. The processes include selecting a Type 60 Nitinol sheet or bar that has been hot-worked at a temperature of above about 900° C. to a reduction of at least 2% in the dimension of said hot-working. Blade blanks are cut from the sheet, and the blade blanks are heated to between 600° C. to about 800° C. and immediately quenched to ambient temperature to produce blanks having a hardness of about 48-53RC. The running edge of the blade blanks a ground to a desired profile and sharpness. The ground blades may then be heated to an elevated temperature of about 850-1000° C. and immediately quenched to produce a hardness at the edge of above 56RC.

This is related U.S. Provisional Application No. 60/358,988 filed onFeb. 21, 2002 and entitled “Nitinol Ice Blades” and to U.S. ProvisionalApplication Nos. 60/210,902 and 60/265,562 filed on Jun. 11, 2000 andJan. 31, 2001, respectively, and U.S. patent application Ser. No.09/879,371 filed on Jun. 11, 2001, which issued as U.S. Pat. No.6,422,010 on Jul. 23, 2002, entitled “Manufacturing of Nitinol Parts andForms”, and U.S. Provisional Application 60/036,784, 60/029,251,60/011,648 filed on Jan. 28, 1997, Oct. 24, 1996, and Feb. 14, 1996,respectively, perfected as PCT/US97/02324 on Feb. 14, 1997 and U.S.patent application Ser. No. 09/125,218, issued as U.S. Pat. No.6,293,020 on Sep. 25, 2001, and Divisional application Ser. No.09/926,978 filed on Sep. 24, 2001.

This invention relates to Nitinol ice skate blades that have superiorerosion resistance, toughness, low sliding friction on ice, andexcellent corrosion resistance, and to processes for produce them.

BACKGROUND OF THE INVENTION

Ice skating is a widely popular sport in many countries. The evolutionof skating has led to many innovative changes in the hardware used inthis sport. These innovations include improved designs for skate bladesand the metals used for the blades. Existing ice skate blades arepresently manufactured from high carbon steels, stainless steels ortitanium. Each of these materials has characteristics that areundesired. Corrosion resistance is an important characteristic for iceskate blades. As a blade corrodes, the cutting edge deteriorates, thusbecoming dull. When skate cutting edges are dull, they do noteffectively cut into the ice. Sharp cutting edges are important,especially when a skater is making turns. Presently, it is not uncommonfor hockey players to grind their skates twice during a competitiongame. All skating rinks have grinding equipment to provide for theregrinding of blades. Improvements in the ability of ice skate blades toretain a sharp edge and resist corrosion would be an important factor inthe sports of hockey, speed skating and figure skating.

High carbon steels are subject to corrosion and thus dulling of therunning surface of the blade. Stainless steels have better corrosionresistance properties than the high carbon steel blades however, arestill subject to corrosion. Corrosion is the primary reason for thedulling of steel ice skate blades. Thus, if a blade had good corrosionresistance, the time between re-grinding could be reduced.

Ice skate blades produced from high carbon steel are normally platedwith chrome or other corrosion resistant materials. This platinghowever, cannot be applied to the running surface of the blade as theyare constantly being re-ground to produce two ice cutting edges.Stainless steel blades have better corrosion resistance than high carbonsteel, but in order to be heat treatable to high hardness, substantialcarbon content in the alloy is required. This high carbon contentincreases the potential for corrosion.

Titanium skate blades do have good corrosion resistance properties.However, titanium cannot be processed to have high hardness. Titaniumcan be processed to have a maximum hardness of ˜38 Rockwell C.

An important consideration when selecting a skate blade material,besides hardness of the metal surface that rides on the ice, isbrittleness. The skate blade material must be hard enough to minimizeerosion of the blade, but not so hard as to be brittle. Hockey blades,especially, must be malleable enough to absorb impacts withoutshattering.

A third factor, not commonly considered for conventional skate bladedesign, is the coefficient of friction of the blade on the ice. Skateblades concentrate the weight of the skater in a small area and theresulting pressure produces a film of water, which lubricates the skateblade as it slides over the ice surface. However, there is solid icecontact on skate blade edges during skating, particularly during turningand hard edging while accelerating forward. Improvements to thecoefficient of friction of the skate blade on the ice would improve thespeed and smooth feel of the skates and would be an improvement muchwelcomed by skaters.

The same characteristics would also be useful for other ice slidingequipment such as sleds and ice boats, and on other sporting vehiclesintended for use on ice, such a luge, bobsled and skeleton.

SUMMARY OF THE INVENTION

Accordingly, this invention provides a Nitinol ice blade and processesfor manufacturing a Nitinol ice blade that provides capabilitiesunavailable in current blades or any known-variant of current blades. Inparticular, I contemplate the use of Nitinol as hockey, figure and speedice skating blades. Although both the Type 55 and Type 60 Nitinolmaterial can be used for blade fabrication, the preferred material isthe Type 60. Type 60 can be processed to have high hardness (up toRockwell 62C), has excellent toughness properties, a weightapproximately 16% less than steel, superior corrosion resistance, andcan be polished to have mirror finishes.

The Nitinol skate blades of this invention run faster on the ice, turnbetter, and last longer between sharpenings than any skate blade everknown to man. Moreover, they are lighter and chatter less on the icethan current state-of-the-art skate blades. These Nitinol skate bladesare corrosion resistant so they will not rust like steel blades betweenuses, and they have a lower Young's modulus and a higher dampingcapacity than steel, so they tend to hold their grip on the ice betterthan steel blades. They have a lower coefficient of friction on the icethan steel and they can be heat treated to have a very smooth and hardoxide finish on the side edges that is even harder and smoother, and hasa lower coefficient of friction to produce exceptional runningproperties on the ice. Type 60 Nitinol can be processed to have ahardness of up to 62 Rockwell C, superior erosion resistance, toughness,and is virtually corrosion proof in the environment of a skating rink.Type 60 Nitinol blades can run on ice approximately five times longerthan existing steel blades before re-grinding is required.

The invention includes processes for manufacturing Type 60 Nitinol skateblades. They are cut by available economical cutting processes such aslaser or abrasive water jet from rolled Type 60 Nitinol sheet orextruded Type 60 Nitinol bars, and are heat treated to reducebrittleness and improve toughness and impact strength, and give theskate blade an elastic property which I call “ultraelasticity”.

The part may be machined to reduce it to near net size, and may beground to reduce the part to the exact specified part size. For example,flat stock can be surface ground. For parts requiring a smooth surfacefinish, polishing or lapping provides the specified surface finish onthe part, down to 0.5 microinch RMS or finer. The part may be heattreated to obtain the desired hardness, from RC40 to RC65.

An integral surface oxide of any of several colors can be formed on thesurface of the part. The oxide surface may itself be polished to an evenfiner surface finish. These process elements may all be used to producea particular part that requires the characteristics provided by eachprocess element, and they may be used in combinations that omitparticular process elements or substitute others to give the desiredcharacteristics of the part.

The unique physical characteristics of Type 60 Nitinol make it the idealmaterial to be used for ice blades, and ice skate blades, in particular.The corrosion resistance of the material ensures that blades made fromNitinol will never rust when used on ice. Corrosion of existing steeland stainless steel is a major cost factor to the ice sport industry.Presently, the manufacturers of high carbon steel blades apply chromeplating to the blades in an attempt to reduce the effect of corrosion.The problem this approach is that the runner (bottom) of the blades areperiodically ground to resharpen the edges, which of course removes thechrome plating. After exposure to the ice (water) the bottom of theblade corrodes, and thus dulls rapidly. This corrosion process alsooccurs on stainless steel blades, although it takes longer. Salt forcorrosion tests performed on high-carbon steel showed signs of corrosionin salt water within eight minutes, and four hours on 440C typestainless steel. The same tests performed on Type 60 Nitinol showed nocorrosion after several thousand hours of exposure to salt fog.

DESCRIPTION OF THE DRAWINGS

The invention and its many attendant benefits and advantages will becomebetter understood upon reading the following detailed description of thepreferred embodiments in conjunction with the following drawings,wherein:

FIG. 1 is an exploded elevation of a hockey ice skate having a Nitinolskate blade in accordance with this invention;

FIG. 2 is an exploded elevation of a hockey ice skate blade holder andskate blade exploded out of the holder;

FIG. 3 is an end view of the skate blade shown in FIG. 2;

FIG. 4 is an end elevation of the skate blade mounted in the holdershown in FIG. 2;

FIG. 5 is a is an elevation of a figure skate having a Nitinol skateblade in accordance with this invention;

FIG. 6 is a sectional elevation of the Nitinol skate blade shown in FIG.5;

FIG. 7 is an end sectional elevation of one version of the skate bladeshown in FIG. 5;

FIG. 8 is an end sectional elevation of another embodiment of the skateblade shown in FIG. 5;

FIG. 9 is an elevation of a speed skate blade in accordance with thisinvention; and

FIG. 10 is a sectional elevation of the skate blade shown in FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designatethe same or corresponding parts, and more particularly to FIGS. 1 and 2thereof, a hockey skate 20 is shown having a boot 23 and a blade holder26 in which a skate blade 30 in accordance with this invention isremovably mounted. The skate blade 30 has attachment structures 32 forengaging complementary structures 34 on the blade holder 26 to securelyattach the skate blade 30 to the blade holder 26. These structures 32and 34 are conventional and are well known to those skilled in the art.

A figure skate blade 40, shown in FIG. 5, has a Nitinol edge 44 attachedto a Titanium or stainless steel blade body 42 by welding, such as laserwelding. The edge 44 can also be fitted into a groove in the blade body42 as shown in FIG. 7, or can be fitted around the blade body in achannel shaped edge 44′ as shown in FIG. 8.

A speed skate blade 50, shown in FIG. 10, has a skate body 52 withconventional attachment structure for attaching the blade 50 to a speedskate boot. It could alternatively have the now conventional clapskating structure that attaches the blade to the skate boot with apivotal attachment. A Nitinol edge structure 56 fits into a groove inthe skate blade 50 is attached to the blade 50 by attachment structure58.

As used herein, the term ice blade and ice skate blade is intended toencompass other types of apparatus and equipment that slide on ice, suchas sleds and ice boats, and sporting vehicles intended for use on ice,such a luge, bobsled and skeleton.

Nitinol is a nickel-titanium intermetallic compound invented at theNaval Ordinance Laboratory in the early 1960's. It is a material withuseful properties, but manufacturers who have worked with it have hadlittle success in making Nitinol parts and semi-finished forms. BecauseNitinol is so extremely difficult to form and machine; workers in themetal products arts usually abandoned the effort to make-products out ofanything except Type 55 Nitinol drawn wire because the time and costsinvolved did not warrant the paltry results they were able to obtain.

Type 60 Nitinol (60% Nickel and 40% Titanium by weight), has manyproperties that are unrecognized as of potential value. It can bepolished to an extremely smooth finish, less than 1 microinch rms. It isnaturally hard and can be heat treated to a hardness on the order of62Rc or higher. It can be processed to have a very hard integral complexoxide surface that can itself be polished to an even smoother surfacethan the parent metal. It is non-magnetic, immune to corrosion from mostcommon corrosive agents, and can be treated to have a high yieldstrength and toughness, even at elevated temperatures. It is 26% lowerdensity than steel for weight sensitive applications such as aircraft,satellites and spacecraft. However, there has hitherto been littleeffort in making useful parts out of Type 60 Nitinol because it is sodifficult to work, because it was known to be brittle, and because therehas been no known method to make parts and forms out of it.

Type 60 Nitinol can be hot rolled from a cast billet by successive hotpasses through a rolling mill. It can be successfully rolled at atemperature of about 900° C. to 950° C. to a reduction of at least about2% per pass in the dimension of the hot-working. The polled sheet isnormally hard and brittle without subsequent heat treatment.

To make ice blades, as illustrated in FIGS. 11 and 12, a Type 60 Nitinolsheet or plate 60 that has been hot-worked as noted above, or anextruded bar 62 shown in FIG. 12, is selected and blade blanks 64 arecut out of the sheet. They are cut by available economical cuttingprocesses such as laser or abrasive water jet from rolled Type 60Nitinol sheet 60 or extruded Type 60 Nitinol bars 62, and are heattreated, as described below, to reduce brittleness and improve toughnessand impact strength, and give the skate blade an elastic property whichI call “ultraelasticity”.

Nitinol ice skate blades must be processed to be both tough and hard.The hardness and toughness of the blades is achieved in accordance withthis invention by a heat treatment process. The optimum hardness of theblade strong back is 48 to 53 Rockwell C. The hardness of the bottom ofthe runners can be processed to have a higher hardness (up to 62 Rc) ifdesired.

The high toughness properties of Type 60 Nitinol can be achieved byheating the blade blanks in an oven to between 600° C. and 800° C.,preferably about 700° C. ±20° C., and then rapidly quenching the blankin a coolant such as oil or water. This yields the desiredcharacteristics of high hardness and toughness for the blade blanks. Theoptimum hardness for the blades is 49 to 53 Rockwell C and a yieldstrength of over 120,000 psi.

The surface of the blade that contacts the ice can be heat treated tohave high hardness, up to 62 Rockwell C. The process consists of heatsinking the strong back of the knife and heating only the contactsurface to approximately 900 to 1000 degrees C°, for example, with anacetylene torch, induction coil, or other localized heating process, andthen rapidly quenching the blade in water or oil.

The blade blanks 64 are finish ground to the desired final dimensions tofit properly in the blade holders 26. Prior to grinding the skate bladeblanks 64 to the desired thickness, they should be flattened. Type 60Nitinol parts may be shaped to a desired contour without spring-back bya process involving forming the part to the desired contour and heattreating it while holding it at the desired contour. One technique forperforming this process is to heat the blade blanks in a furnace or ovenat a temperature of 600° C.-800° C., preferably 700C°. The skate bladeblanks are laid onto a thick steel plate, having a flat top surface, inthe furnace, and another thick steel plate, having a flat bottomsurface, is placed on top of the blade blanks. The assembly is insertedin a preheated oven and, after temperature equalization, the parts areheld at the 700° C. temperature for a minimum of fifteen minutes. Theblade blanks are then removed and immediately quenched in a water bath.The blade blanks should be held vertical when quenched in the water tominimize warping of the blade from uneven cooling. It is also desirablethat the time between removal of the blade from the furnace andquenching be as short as possible. The time lag between furnace removaland quenching should be within about twenty seconds, preferably within15 seconds from removal from the oven. In order to minimize the time lagbetween removal of the blanks from the oven and the quenching operation,it is convenient to locate the quenching tank close to the oven. Thisshort lag time is useful to maintain the temperature of the blade closeto 700° C. at the start of the quench process. This process aligns thecrystals within the material and produces a flat tough Nitinol iceblade. The hardness of the blade at this point in the manufacturingprocess is about 48 to 51 Rockwell C.

The flat blade blank is now ready to be ground to the requiredthickness. The preferred method to grind the blades is to run themthrough a “timesaver machine”, which is a large belt grinder. To obtaina good finish on each side of the blade they should be ground on bothsides. The preferred grinding belts to be used are those made from agrinding media called Cubatron, a 3M company product. Cubatron belts of60 grit are preferred, although other grid sizes can be used. A lightpressure and shallow grinding passes are preferred because they producelittle heat increase and do not cause significant rounding of thecorners. When the blades are at the required thickness, final polishingmay be accomplished using another 3M timesaver belt called Trizak. Othertypes of grinding media can also be used obtain the required bladethickness, however the above described grinding media is preferred.

Upon completion of the above grinding operations the blades are readyfor final processing. The final processes insure that all metallurgicalchanges produced by the cold work that was applied by the timesavergrinding operations is removed, applies the black oxide finish onto thesurface of the blades, and insures toughness in the blades.

This final process is identical to the heat treatment used to flattenthe blade. All residue from the grinding operations is removed prior tothe blades being installed in the oven. The oven is preheated to the700° C., the blades installed between the two steel plates with flatfacing surfaces, and the temperature held for approximately fifteenminutes after equalizing. The blades are then removed and quenched asdescribed above.

A hard and slippery black oxide finish is produced with this process.The oxide finish may then be polished to an extremely smooth finishusing a buffing wheel with diamond paste orjewelers rouge.

The oxide finish produced during the above-described processes is hardand non-electrically conductive, which prevents conventional electrochemical etching processes to be used to apply engraving on the blades.Logos, part numbers, or designs on the blades may be applied afterformation of the oxide surface material by laser engraving, or may beapplied after polishing and before oxide formation by electro-chemicalengraving.

Type 60 Nitinol skate blades rarely, if ever, need sharpening. Theice-contact edge is so hard and abrasion resistant, that there is verylittle abrasive wear of the edge material. Moreover, the material isessentially corrosion-proof, so there is no significant corrosion of theice-contacting edges, which is the primary cause of edge dulling inconventional skate blades. However, grinding of the running surfaces ofthe skate blades is necessary during manufacturing and may occasionallybe desirable after an extended period of hard use. On some blades ahollow grind is used, for example hockey skate blades. On other types ofblades a flat or wedge grind is preferred. Grinding and final forming ofthe blades may be performed on a conventional skate blade sharpeningmachine such as a “Blademaster” three station skate sharpening machinemade by Guspro Inc. in Chatham, Ontario, Canada. Conventional skateblade grinding equipment, such as the Blademaster, uses silicon carbideblades and diamond hones for the final pass. For Nitinol skate blades inaccordance with this invention, the process is similar but differs insignificant aspects, noted below. Conventional blade grinding wheels maybe used to grind the Type 60 Nitinol skate blades, but the process islengthy and the conventional grinding wheels wear down quickly. Cubitrongrinding wheels, newly available from Cincinnati Milicron Company inCincinnati, Ohio, are preferred. To minimize excessive heating of theskate blade bottom edge during grinding, it is preferrable to grind inrapid shallow passes of about 0.002″-0.003″. A diamond hone may be usedas a final pass to produce a very smooth finish and especially sharpedges. The diamond hone may also be used to sharpen the blade edgesafter extended use, but should be applied with light pressure to avoidpulling the diamond particles out of the hone.

Permanent marking of the blades, part numbers, logos, serial numbersetc, can be accomplished using electrochemical etching or laserengraving processes. If chemical etching is to be used, the markingsshould be applied prior to the application of the oxide film because theoxide is an effective electrical current isolator and interferes withthe electrochemical etching process. Laser etching processes however,work well on both the uncoated and coated material.

The ultraelastic Type 60 Nitinol workpiece may be heat treated to adesired combination of hardness and elasticity. For example a hardnessof about 58RC-64RC may be obtained by heating it to about 900° C.-950°C. and then quenching in water or other coolant such as oil to cool itquickly to a temperature below about 500° C. The coolant should beagitated or the part moved in the coolant bath to ensure a flow ofcoolant over the surface of the part to ensure even cooling and preventdevelopment of an insulating steam cushion over portions of the part.The hardness can be tailored by the temperature of the initial heating.Rapid quenching produces a surface hardness of about. 58-64RC at somesacrifice to the elasticity of the material. The strength of theultraelastic Type 60 Nitinol heat treated to about 50-55 Rockwell C anda strength of about 140,00-155,000 psi and has an elastic straincapability of about 3% up to about 6%.

To retain the ultraelastic properties in a portion of the workpiece buthigh hardness in other portions such as the edge of a ice skate blade,the portion that need not be hardened can be clamped in a heat sink andthe other portion, such as the ice-contacting edge, is heated to ahardening temperature of 900° C.-950° C. and then rapidly quenched inwater or other coolant. The heat sink prevents the unhardened portionfrom being heated to the hardening temperature so it retains itsultraelastic properties.

Tests performed on 60 Nitinol Hockey blades showed substantiallyimproved results. Hockey skaters stated the blades provided improvedturning and much higher speeds on the ice. The testers also used theblades for extended periods of time without the need for frequentre-sharpening.

Obviously, numerous modifications and variations of the preferredembodiment described above are possible and will become apparent tothose skilled in the art in light of this specification. For example,the ice skating blade in accordance with this invention could be usedfor improved speed and control on sleds and ice boats, and on othersporting vehicles intended for use on ice, such a luge, bobsled andskeleton. Moreover, many functions and advantages are described for thepreferred embodiment, but in many uses of the invention, not all ofthese functions and advantages would be needed. Therefore, I contemplatethe use of the invention using fewer than the complete set of notedfeatures, process steps, benefits, functions and advantages. Forexample, all the process elements may be used to produce a particularpart that requires the characteristics provided by each process element,or alternatively, they may be used in combinations that omit particularprocess elements or substitute others to give the desiredcharacteristics of the part. Moreover, several species and embodimentsof the invention are disclosed herein, but not all are specificallyclaimed, although all are covered by generic claims. Nevertheless, it ismy intention that each and every one of these species and embodiments,and the equivalents thereof, be encompassed and protected within thescope of the following claims, and no dedication to the public isintended by virtue of the lack of claims specific to any individualspecies. Accordingly, it is expressly intended that all theseembodiments, species, modifications and variations, and the equivalentsthereof, in all their combinations, are to be considered within thespirit and scope of the invention as defined in the following claims,wherein I claim:

1. An ice skate blade, comprising: an elongated blade body having a mainblade portion and an edge portion made from Type 60 Nitinol; said edgeportion of said blade body having an ice-contacting bottom edge; saidmain blade portion having structure for engaging a blade holder; saidbottom edge having opposed corners that are sharpened to bite into iceto facilitate travel and maneuvering on said ice; said main bladeportion having an impact strength of greater than 45 foot-pounds and ahardness greater than about 40 RC.
 2. An ice blade as defined in claim1, wherein: said main blade portion has a tensile strength of greaterthan 130KSI and an elastic elongation of more than 3%.
 3. An ice bladeas defined in claim 1, wherein: said blade body has a hardness betweenabout 48RC and 55RC.
 4. An ice blade as defined in claim 1, wherein:said ice blade is an ice skate blade, and said blade holder is affixedto an ice skate boot; said structure for engaging a blade holderincludes structure on a top edge, opposite to said bottom edge, forengaging said blade holder of said ice skate boot.
 5. A method forsharpening a running edge of a Type 60 Nitinol ice skate blade toproduce a hollow grind with opposing sharp edges, comprising: grindingsaid running edge, using a grinding wheel made substantially ofcubitron, to a desired hollow profile with said desired sharp edges,making shallow grinding passes of about 0.002-0.004″ for each pass untilsaid desired sharp edges are attained.
 6. A method of making ice blades,comprising: selecting a Type 60 Nitinol sheet that has been hot-workedat a temperature of about 900° C. to 950° C. to a reduction of at leastabout 2% in the dimension of said hot-working; cutting ice blade blanksfrom said sheet; heating said blanks to between 600° C. to about 800° C.and immediately quenching said blanks to ambient temperature to produceblanks having a hardness of about 48-53RC; and grinding one edge of saidblade blanks to a desired profile and sharpness.
 7. A method as definedin claim 6, further comprising: heat treating of the bottom of the bladeto produce a very hard and erosion resistant surface.
 8. A method asdefined in claim 7, wherein: said heat treating of said bottom of saidblade includes heating said one edge to an elevated temperature of about850-1000° C. and immediately quenching said blade blank to produce ahardness at said one edge of above 56RC.
 9. A method as defined in claim6, wherein: said grinding step includes rotating a narrow grindingblade, made primarily of cubic boron nitride, against said one end ofsaid blade blanks and grinding off a layer of Nitinol in several passes,each pass being at a depth of 0.015″-0.020″.
 10. A method as defined inclaim 6, further comprising: heating said part to a temperature above700° C.; placing said part between matched dies having a die interfaceprofile corresponding to said desired shape; and holding said part atsaid temperature for a period of at least about 15 minutes.
 11. Themethod as defined in claim 9, further comprising: immediately after saidholding period, rapidly quenching said part in coolant from saidtemperature to a temperature below about 400° C.
 12. The method asdefined in claim 10, wherein: said part is an ice blade and said desiredshape is flat.